For some time now, it has been known by the medical profession that certain drugs may be administered to patients by being absorbed over a period of time directly through the epidermis or skin of the patient without using a hypodermic syringe or other invasive technique. Drugs that are intended to be administered in this manner may be compounded in a matrix of other materials suitable for contact with the skin of the patient. One technique for doing so is to combine the drug to be administered transdermally with a pressure sensitive adhesive which can be firmly attached to the skin in a manner which will assure excellent contact with the skin and allow migration of the drug from the pressure sensitive adhesive transdermally to the body of the patient. When this technique is employed, the structure of the article of manufacture includes a backing to protect the pressure sensitive adhesive from contact with other objects and to prevent loss of the drug. Also included is a release liner which is to be removed from the pressure sensitive adhesive immediately prior to application thereof to the skin of the patient. The structure of such transdermal drug delivery devices is shown and described in our application Ser. No. 407,874, now U.S. Pat. No. 5,032,207, issued Jul. 16, 1991.
In order to facilitate practical and economical manufacture and use of such a transdermal device, it has been found useful to score the release liner so as to permit said liner to be easily removed from the adhesive carrying drug in one step. Our prior related applications describe various techniques and apparatus to accomplish this objective of scoring the liner to permit said liner to be easily removed from the drug-containing pressure sensitive adhesive. However, continuing development for improved manufacturing efficiency and operational considerations has resulted in improvements and variations to that described in the earlier cross-referenced applications. Accordingly, this application is directed to a reflection of those improvements.
Several apparatus and methods are believed to have been devised for intermittently or continuously scoring the release liner portion of a transdermal drug delivery device in order to permit said liner to be easily removed from the drug-containing pressure sensitive adhesive disposed between the release liner and the backing in such devices. The liner is, of course, removed from the device immediately prior to its being applied to the skin on the patient. The typical procedure for the preparation of a transdermal drug delivery device involves a plurality of steps. First, a dilution or suspension of the adhesive is compounded with an appropriate concentration of the drug and is applied to a flexible layer intended to function as a disposable release liner, frequently made of plastic. This release liner also forms, during processing, the means to carry a pressure sensitive drug-containing adhesive through the manufacturing and cutting operation thereafter. Next, a non-releasable or primed backing material is applied over the adhesive. The result is a laminate in the form of a web containing an adhesive with a backing on one side and a disposable release liner on the other side. A shaped and precisely sized device is then formed by peripheral cutting through all the layers of the resulting web. The disposable release liner can then be removed and a second, scored release liner can be attached to the transdermal drug-containing adhesive.
Alternatively, the liner can be first scored and assembled with the adhesive and the backing and then the laminate web cut to the desired dimensions.
The purpose of the multi-step procedure for applying the backing and the release liner to the adhesive containing the drug is to avoid problems encountered when a scored release liner is used in processing. If a completely cut release liner is used prior to coating, the drug-containing adhesive can pass through the release liner at the score causing equipment problems, cracking, separation, heat damage, loss of raw materials, and possible exposure of factory workers to the drug or similar environmental concerns.
Moreover, these prior art methods suffer from the disadvantage that the procedure for applying the release liner requires several steps, and thus have a tendency to be more expensive in mass production than a procedure which involves fewer steps.
In one aspect, the present invention overcomes the difficulties and disadvantages associated with prior art devices by providing a method and apparatus for simultaneously cutting an assembled transdermal drug delivery device from a web comprising a backing layer, a drug-containing pressure sensitive adhesive and a release liner while at the same time scoring the release liner at a position intermediate to the periphery of the transdermal drug delivery device.
In another aspect, the present invention overcomes the difficulties and disadvantages associated with prior art devices by providing a method and apparatus for sequentially first scoring the release liner of an assembled transdermal drug delivery device from a web comprising a backing layer, a drug-containing pressure sensitive adhesive and a release liner, and thereafter cutting the transdermal drug delivery device from the web.
Accomplishing the objectives of this invention is achieved, in part, by providing two types of cutting edges, one sized to cut completely through the periphery of the laminate web to size and form the transdermal drug delivery devices, and a second type sized to only cut or score the release liner at a position intermediate to the periphery, and which intermediate or center scoring does not extend all the way to the adhesive nor to the non-releasable backing. These advantages are accomplished by the use of the first type of cutting edges having the configuration and size of the transdermal drug delivery device to be cut from the web which cutting edges are sufficient in dimension to cut completely through the web and thus through the backing, adhesive, and release liner layers. At the same time, the second type or intermediate or center portion cutting edge is sized to score the release liner to a point just short of the adhesive liner or through the release layer, but not to the adhesive.
There are, of course, prior art devices which relate to apparatuses for scoring or cutting material in the form of a sheet, even when the same is formed from a laminated product. For example, Forbes, Jr., U.S. Pat. No. 3,786,732, relates to an apparatus for scoring a sheet like material. However, it refers to the scoring of carton blank material. The material thereby scored, is substantially different from a pressure sensitive adhesive containing laminate having a degree of dimensional instability and less resistance to cutting action. It is recognized that the apparatus of Forbes, Jr. does not teach a formation for cutting of a drug-containing pressure sensitive adhesive sandwiched between a backing layer and a release liner.
Another prior art reference is Woodall, U.S. Pat. No. 1,963,393, which relates to the cutting of a laminated panel, particularly for a sun visor, to protect automobile drivers. The disclosure relates a panel formed of a sheet of thermal plastic material, which has a fabric on one side attached by an adhesive.
However, both of these references constitute non-analogous prior art, because one skilled in the art attempting to construct a nearly paper-thin transdermal drug delivery device, substantially in the form of a bandage, and having a dimensionally unstable cross-section, would not expect to look for guidance in the arts of cutting and scoring laminated panels or sheet materials. The laminate of the subject transdermal drug delivery device includes one relatively hard surface, i.e., the release liner, a soft or flexible surface, i.e., the backing layer, and a dimensionally unstable inner layer, i.e., the drug-containing pressure sensitive adhesive.